The proton ruby gem and package are incorrectly named according to the standard gem naming rules, see https://issues.apache.org/jira/browse/PROTON-1760 for details.
The short story is we want to change the name from "qpid_proton" to "qpid-proton" for the next release (0.22, not the 0.21 release in progress) The impact is that code using the package would need to change lines `require 'qpid_proton'` to `require 'qpid-proton'`. It's annoying, but it seems best to get it right as quickly as possible. The plan is be to leave the "qpid_proton" gem available, but stalled at version 0.21. Code using the "qpid_proton" gem won't break but to avail of future updates you'll need to switch to using the "qpid-proton" gem instead. If you're using ruby from a downloaded source package or git clone you'll need to update your code to use the 0.22 release. I'll make the change next week - I want to make it early in the release cycle so we have time to find and iron out problems. If anyone has questions, problems or suggestions about how to make the transition smoother please respond to the list or comment on the JIRA https://issues.apache.org/jira/browse/PROTON-1760 Cheers, Alan.